Final answer:
In the first trophic level of a food chain, the producers are present, which include photosynthetic organisms like plants and phytoplankton.
Step-by-step explanation:
The organisms present in the first trophic level are known as producers. Producers are typically photosynthetic organisms such as plants and phytoplankton. They form the foundation of ecosystems by converting energy from the sun into organic compounds that can be used by other organisms. This process supports the entire food web, as producers are consumed by primary consumers (herbivores), which are then preyed upon by secondary consumers (carnivores). Tertiary consumers are carnivores that eat other carnivores, and higher-level consumers, including the apex consumers, sit at the top of the food chain.